Ash dieback

Ash dieback is a fungal disease that prevents ash trees from taking up water and minerals from their roots, causing leaf loss, dying branches and ultimately death. Infected trees become progressively fragile, often succumbing to secondary infections which have the ability to effect stability.

It is estimated that the disease will kill up to 90% of all ash trees in the UK, over the next decade. There is currently no cure or method of control to prevent or protect against it, which means trees that have succumbed to ash dieback must be felled. Some ash trees on Horsham District Council land have already been killed by the disease and have been felled in the past couple of years.

What ash dieback looks like

Ash trees that have become infected may display a range of symptoms but most obvious are dead twigs or branches with no leaves in the summer (June to September).  The disease weakens the tree over time, with the canopy becoming thinner and thinner.

In this aerial shot of Horsham District Council land, the dying ash trees are clearly identifiable.

An aerial view of ash trees on Horsham District Council land. The ones affected by ash dieback are clearly identifiable by their leafless branches

How we are tackling ash dieback on Horsham District Council land

There are thousands of ash trees on Horsham District Council land, both within woodland and parks and open spaces. More and more of these trees are showing the symptoms of ash dieback and the Council is working on a plan of action for the worst affected sites.

We can only deal with trees on Horsham District Council-owned land. West Sussex County Council has a programme to deal with ash trees next to public roads. Private landowners who have ash trees on their own land must take responsibility for monitoring the condition of their trees.

From this winter, and for the next few years, we will be removing diseased and dying ash from many of our sites, including Warnham Local Nature Reserve and Southwater Country Park. This will be a phased approach, targeting woods in order of the urgency of the work.

Some of our woods are between 30-50% ash, so their removal will have a significant impact on the landscape, but this is unavoidable.

How we decide when to fell an infected tree

It is inevitable that we will need to fell infected trees on Council land that may cause harm to users of our sites, or to neighbouring property. We monitor trees on our land on a regular basis, with the interval between inspections dependent on the site location and history. We are trailing aerial survey using a drone, to inspect the canopy of seriously affected woodland areas from overhead.

We can track the progress of ash dieback in an individual tree by the loss of the canopy and amount of dead wood visible.  We want to retain ash trees for as long as possible to see if they have natural resistance. However, once approximately 40% or more of the canopy has been lost, the tree is succumbing to ash dieback and will need to be felled. In some cases it will be necessary to fell a small number of healthy trees as part of the overall process to allow access into a wood, or to ensure dangerous trees can be felled safely. In some cases the trees will be left where they fall, in others the timber may be removed – it will depend on a site-by site basis.

Before we start work

Before we start felling works in a block of woodland we need to obtain a felling licence from the Forestry Commission, unless the trees are already dead or presenting a risk to persons or property.

Where a significant amount of felling is due to take place, we will contact residents who neighbour the land and provide more detailed plans for that site. Information notices will be put on-site, and we will update this webpage with as much information as possible. Please be aware, we will not be able to do this if we fell a single tree or a small clump.

Timescales and locations

We expect to be dealing with ash dieback for the next five years or so, as more trees become infected. We intend that most of the woodland felling should take place in the winters, but trees may be felled at any time during the year, if we believe there is a risk to public safety.

Work will start this winter 2021-22 with an area of woodland in North Horsham. Other areas with significant amounts of ash include Warnham Nature Reserve and Southwater Country Park.

Further information on ash dieback

Ash dieback control in Walnut Plantation, Warnham Local Nature Reserve

Ash dieback control work will take place in Walnut Plantation, Warnham Local Nature Reserve, during autumn/ winter 2022. The highlighted area on the map indicates where Ash dieback control work will take place.

The frequently asked questions detailed below are specific to this location.

Walnut Plantation Ash Dieback

Completed Ash dieback works

Ash dieback control work has already taken place in  Bartholomew Way, Horsham ( January 2022). The highlighted area on the map indicates where Ash dieback control work too place take place.

A map indicating the area of Bartholomew Way Horsham where ash dieback control work will take place

Additional work took place in Granary Way, Horsham (February 2022.)

The highlighted map indicates where ash dieback control work took place.

Ash dieback work in Granary Way